Radio frequency (RF) antennas are used in a variety of devices to transmit and receive communications. Many applications have strict space and volume restrictions and require antennas that function efficiently, but that are relatively small. This is especially the case with mobile devices, such as cellular phones, radio frequency identification (RFID) tags, and mobile handheld devices.
To maintain a low profile some devices employ an inverted-F antenna. This antenna has a low profile because the radiator arm is parallel to the ground plane, rather than perpendicular, as is the case with most antennas. U.S. Pat. No. 6,222,496 issued to Liu teaches an example of an inverted-F antenna.
Another option for reducing the size of antennas is to employ a meander-line antenna. The meander-line antenna is a conventional antenna that features a winding back-and-forth topology, as shown in FIG. 4 herein. Constructing the antenna such that it winds back and forth in a switchback fashion helps to conserve space and retains a relatively high radiation resistance as compared to other winding configurations, such as a helix antenna. An even more compact meander-line antenna is described in U.S. Pat. No. 6,630,906 issued to Tomomatsu et al., which teaches forming a dielectric block around part of a meander-line antenna and then folding the exposed portion of the meander-line antenna around the dielectric block.